Optical Coherence Tomography (OCT) is a technique to measure depth dependent refractive index changes at a single location, and can be used for two- and three-dimensional imaging of tissue and other semi-transparent materials. 3D OCT is primarily used in the eye, to image the retina and retinal abnormalities and the cornea and corneal abnormalities at high resolution. The principle of OCT is based upon low-coherence interferometry, where the backscatter from more outer retinal tissues can be differentiated from that of more inner tissues because it takes longer for the light to reach the sensor. Because the differences between the most superficial and the deepest layers in the retina and the cornea are around 100-400 μm, the difference in time of arrival is very small and requires interferometry to measure. The spectral-domain OCT (SDOCT) improvement of the traditional time-domain OCT (TDOCT) technique, known also as Fourier domain OCT (FDOCT), makes this technology suitable for real-time cross-sectional retinal imaging at video rate.
OCT imagers presently on the market are expensive and complex because they depend on scanning across the retina, which is typically performed through galvanic mirrors that deflect measurement light. Galvanic mirrors require precise adjustment, have finite latency and response time, and substantially increase complexity and cost of OCT imagers. Because of this substantial cost and complexity, the availability of OCT imagers is limited and thus many in the population have limited access to retinal examinations that could be key to the early detection and preventative treatment of conditions such as diabetic retinopathy. There is a need in the art for a low-cost OCT imager that could be cheaply and easily deployed to locations such as primary care clinics, drug stores and retail stores, or even at home to allow for increased access to high quality retinal scans.